The present invention relates to a marking method for displaying characters and graphic patterns on a resin molded piece by energy ray such as laser beam, and a marked resin molded piece.
Conventional marking method on resin molded pieces by laser beam are disclosed in Japanese Patent Publication No. 61-11771 and Japanese Patent Publication No. 62-59663. That is, a mixture is prepared by mixing a filler which changes color by action of laser beam in a resin of base material, and this mixture is molded into a resin molded piece by injection molding method or the like, and this molded piece is irradiated with laser beam to change the color of the filler. Such methods of marking desired characters and graphic patterns are disclosed. Other marking methods are disclosed in Japanese Laid-open Patent No. S60-4094 and Japanese Laid-open Patent No.H1-267092. That is, plural layers of coat films are formed by adhering plural paints having different colors preliminarily on the surface of resin molded piece, and the coat films are irradiated with laser beam, and coat films of only surface layer or plural layers are locally removed. Such methods of marking desired characters and graphic patterns are disclosed.
Such conventional marking methods and marked resin molded pieces are described by referring to FIG. 5 and FIG. 6.
FIG. 5 is a front view for explaining the method of changing the color of the filler in the resin molded piece. In FIG. 5, a laser beam 1 is controlled by a deflector 2. A resin molded piece 3 is a molded piece of a mixture of a resin and a filler 4 such as carbon black or dyexe2x96xa1containingxe2x96xa1silicon which changes color by the action of the laser beam 1. When the laser beam 1 is emitted to the resin molded piece 3 according to a desired character or graphic pattern, the filler 4 in the resin molded piece 3 changes color, and a mark 5 is formed on the surface layer of the resin molded piece 3, so that a marked resin molded piece is obtained.
FIG. 6 is a sectional view of essential parts for explaining a method of removing the coat film of the paint on the resin molded piece. In FIG. 6, a laser beam 1 is controlled by a deflector 2 same as in the case above. On the surface of the resin molded piece 6, three color paints are sequentially applied, and three layers of coat films 7, 8, 9 are formed. The laser beam 1 is deflected and controlled in the emitting position corresponding to a desired character or graphic pattern, and its energy quantity is controlled, and is emitted from the surface coat film 7 side of the resin molded piece 6. Depending on the energy quantity, the coat film 7, coat film 8 or coat film 9 is removed. Thus, a marked resin molded piece marked with character or graphic pattern of desired colors is obtained.
However, in the conventional marking method by making use of color change of the filler 4 of the resin molded piece 3 by laser beam 1, character or graphic pattern marks 5 of different colors cannot be formed on a same resin molded piece 3. Or in the method of removing the coat films locally by irradiating the surface of the resin molded piece 6 having coat films 7, 8, 9 with laser beam 1, by using different colors in the coat films 7, 8, 9, marking of combination of different color marks is possible, but it takes many steps on coating and drying, and the manufacturing cost is very high.
It is hence an object of the invention to present a marking method capable of marking various colors on a resin molded piece inexpensively, and a marked resin molded piece.
The invention is characterized by forming a resin molded piece by combining plural base materials molded and processed from a mixture of a resin and a filler which changes into different colors by irradiation with energy ray, irradiating the surface of the resin molded piece with energy ray, marking irradiated positions with plural colors, and forming a marked resin molded piece.
The marking method of the invention comprises:
(a) a step of forming a resin molded piece by using plural base materials,
in which each one of the plural base materials is formed of a mixture of each filler and each resin, and each filler may be changed into mutually different color by irradiation with energy ray, and
(b) a step of irradiating the resin molded piece with the energy ray, changing the color of the filler at the irradiated position, and forming each color mark,
in which at least two of the different color marks are mutually different in color.
The marked resin molded piece of the invention comprises:
(a) a resin molded piece formed of plural base materials,
in which each one of the plural base materials has each resin and each filler dispersed in each resin, and each filler may be changed into mutually different color by irradiation with energy ray, and
(b) a color mark formed on the resin molded piece,
in which the color mark has a mark changed by color change of each filler at the irradiated position of the energy ray, and at least two of the different color marks are mutually different in color.
Preferably, the resin molded piece is a keytop of a keyboard used in an electronic appliance.
In this constitution, marks having clearly divided plural colors can be formed on the resin molded piece at low cost.